The Detective by Roderick Thorp, 1966
You may have never heard of this book before. Roderick Thorp may have written a dozen novels. He wasn't a genius, a professor, or a prolific author who wrote a book every week. The Detective was adapted into a film starring Frank Sinatra that went well at the box office, but the narrative slipped into obscurity–except for Thorp's sequel to The Detective, Nothing Lasts Forever, which was adapted into the film Die Hard. And perhaps you've heard of it. The Detective is about a New York City detective named Joe Leland who is assigned to investigate a man's death and determine who killed him and why.
Given that it was written in 1966, the book covers some of today's societal challenges and prejudices. It's a large thick book, and while it's probably no longer in print, you can still get a copy of it and read it.
Link to buy: www.amazon.com/dp/0385294697?tag=upjourney-20